Flexible container



Nov. 4, 1941. v H, MAASS 2,261,265

FLEXIBLE CONTAINER Filed Nov. 20, 1957 3 Sheets-Sheet l Nov. 4', 1941.H. MAAss 2,261,265

FLEXIBLE CONTAINER Filed Nov. 20, 1937 3 Sheets-Sheet 2- Patented Nov.4, 1941 FLEXIBLE CONTAINER Herbert Maass, Berlin-Halensee, Germany,assignor to Siemens- Schuckertwerke Aktiengesellschaft,Berlin-Siemensstadt, Germany, a

corporation of Germany Application November 20, 1937, Serial No. 175,734In Germany November 20, 1936 7 Claims.

The present invention relates to fluid systems and, more particularly,to containers of variable volume forming a member of such fluid systemsfor compressing, expanding, pumping or otherwise impelling a fluidmedium.

In the construction of pumps, compressors or the like flexiblecontainers areknown in which two opposite walls are firmly joined witheach other along their periphery and the volume of the container isvaried by moving the central portions of the wall relatively to theplane of the peripheral curve. If the elastic walls of such containerare made of metal, very high stresses occur at relatively smallmovementsso that obtainable variation of volume is rather small and the life ofthe container walls is very limited.

It is an object of the present invention to increase the flexibility ofcontainers of the above type, in order to increase the variable capacityof the container and to reduce the stresses acting upon the materialduring the operation.

According to the invention a considerable increase in flexibility of thewalls of an expansible container for fluid systems is attained bydesigning the wall shape according to certain novel points of view whichwill be understood from the following description of the embodimentsshown in the drawings in which Figs. 1, 2 and 3 are of explanatorynature and serve to illustrate the considerations underlying theinvention;

Fig. 4 exemplifies a shape of the container walls designed according tothe invention;

Fig. 5 shows a modification of a portion of the shape shown in 4, and

Figs. 6 and 7 two other shapes of container walls also corresponding tothe present invention; while Figs. 8, 9 and 10 explain three furtherways of embodying the invention, and

Fig. 11 shows a refrigerator employing a con-' tainer made according tothe invention as compressor for the refrigerant, this illustrationrepresenting a part-sectional view of the upper portion of therefrigerator.

In referring to Figs. 1, 2 and 3, the factors will at first beconsidered which, owing to the shape of the peripheral curve of acontainer of the type here concerned, infiuencethe flexibility of suchcontainer. In Fig. lis shown a plan view of a disk in general shapeintended to form one of the flexible walls of such a container. In thepresent case it is assumed that the disk is to be raised at the point 0out of the plane of illustration and that the periphery of the diskshall remain in this plane. In practice this is accomplished by the factthat the second disk which has the same shape and is joined with theillustrated disk along the common periphery, is correspondingly movedout of the plane of the periphery in the opposite direction.

In considering the two elemental areas OAB and ODE shown in Fig. 1 a rayfrom the point 0 which upon the movement of the disk is moved farthestfrom the plane of the peripheral curve, for instance, the straight lineR1 or R2, is designated in the following as a radius vector, whichstraight line in the case of the elemental areas under consideration isthe bisecting line of the angles 01 and d2 respectively. The radiusvector R1 intersects the peripheral curve under the angle 0'1, theradius vector R2 under the angle c2. s1 and s2 denote the correspondinglength of the arc of the elemental areas under consideration. The angle0'1 amounts to about the angle :72 to about 30.

The elemental areas shown in Fig. 1 are separately considered in Figs. 2and 3, and these elemental areas are drawn in these cases under theassumption that the pointO is raised out of the original plane throughthe height h. The perpendicular projection of the triangular elementalarea OAB in Fig. 2 shows that the angle 11 1 of the elemental area issmaller than the angle 1 of the perpendicular projection.

Since in the case of flat disks a considerable change of the angle isactually not possible and must be taken up by the resiliency of thematerial, the change of angle is a measure for the tangential stressesoccurring during the motion. Since those diaphragms which consist of twoflat circular plates may be considered as composed of single elementalareas of the kind shown in Fig. 2 in which the radius vector intersectsthe peripheral curvealways under an angle of the reductions of theangles are summed. It

follows that the flexibility of such containers is very limited owing tothe high tangential stresses. Since, however, as will be seen from Fig.3, also an increase of the angle is possible, the stresses may beconsiderably reduced by a certain dimensioning of the angle ofintersection.

A considerably greater flexibility of the container is attainedaccording to the invention by the fact that the angle of intersectionbetween the peripheral curve of the disk and the radius vector amountsin average to 45. When designing the disks, in such a manner, theindividual elemental areas of the disks have such a shape that thechanges of the angle at the point taken together are as small aspossible.

In order to obtain a closed peripheral curve for the disk in which theangle of intersection between this curve and the radius vector amountsin average to 45, the periphery may be composed of different elements.For instance, the peripheral curve may be composed of the portions of alogarithmic spiral with an angle of intersection of 45. Such a case isshown in Fig. 4. Here the peripheral curve of the flat plate is composedof portions GH, HI etc. of a logarithmic spiral in which the angle ofintersection 0' between this peripheral curve and any radius vector OKamounts to 45.

In such curve portions of logarithmic spirals the conditions for eachelemental area considered corresponding to Fig. 1 are the saine.However, also other curves may be employed whose angle of intersectionwith the radius vector differs from 45 at certain points. In this casecurve portions Whose angle of intersection is smaller than 45 must beallotted as compensation to such curve portions 'whose angle ofintersection is greater than 45. This compensation must be eifected insuch a manner that the angle of intersection amounts in average'to 45.It follows that in the case of rounded peripheral curves which incertain portions intersect the radius vector under,90, compensatingcurve portions are necessary in which the angle of intersection issmaller than 45.

In Fig. 5 is shown schematically the manner in which the peripheralcurve according to .Fig. 4 may be rounded off. Sp denotesthe'logarithmic spiral and Ah? the rounded off curve. 7

The general law according to which compensating curve portions whoseangle of intersection in certain portions is smaller than 45 must beallotted to such marginal curves whose angle of intersection is greaterthan 45 reads as'follows:

sin n +cos n RY SlD'T 'FCOS T2 R2 The designations used in this equationare indicated in Fig. 1. The angle 1' denotes the departures of theangle of intersection between the marginal curve and the radius vectorfrom 45 according to the formula =a-"-45. The elemental areas OAB andODE in Fig. 1 are so (11- mensioned that the departures of the angle ofintersection n from 45 are compensated for by the elemental area ODEwith the intersecting angle 0'2. According to the 'above-mentioned'law,

therefore, the compensation is to be effected if, r

for instance, as shown in Fig. 5 the logarithmic spiral Sp is to berounded off.

In forming the peripheral curve according to the invention alsorectilinear portions may be employed. These portions may, for instance,be so arranged that the radius vector which bisects the angle 1 (Fig. 1)intersects the peripheral curve under 45. Such a peripheral curve withrectilinear portions is schematically shown in Fig. 6. A central or hubportion N is provided as is generally required in such flexiblecontainers for supporting the container or for securing thereto asuction conduit and a pressure conduit. Such hub portions may, forinstance, be designed with a polygonal cross-section. The plate thencontains angular areas. In Fig.5 the hub portion N of the plate has theform of an hexagon from each side of which extend rectangular areasOADE, OCFG etc.

The average value of the angle of intersection in which the material issharply bent.

case curve portions occur whose angle of intersection is greater than45, the corresponding compensation must be effected by curve portionswhose angle of intersection is smaller than 45 and which lie between twoadjacent rectangular areas. Fig. 6 thus shows a rectilinearly limitedperipheral curve which is so shaped that the bisecting line OH of theangle on and the bisecting line OK of the angle 9 intersect theperipheral portions AB and BC under an angle of 45.

If the periphery is composed of a plurality of spiral or rectilinearportions which abut each other so as to form a pointed angle, thesurface,

as recognizable fromFigs. 2 and'6, when operating thecontaineryassurn'es 'the form of ridges Sucha ridge formation is notpermissible in materials resistant to bending. Consequently, as shown inFig. 5 such peripheral curves'are preferable in which the curve portionscomprising theperiphery are correspondingly rounded off. 'However, theinvention may also be carried into practice in such a manner thatuniformly bent peripheral curves are employed. Since according to theinvention the angle of intersection between the radius 'vector and themarginal curve should amount in average to 45, star-like figures Stsuch'as shown in Fig. 7 are thus obtained.

The provision of a hub area in the case of unifolmly'bent peripheralcurves may be effected by maintaining this uniform curvature in such amanner that 'all radii vectors are lengthenedby the radius of the hubarea in the manner shown in Fig. 7 by a dotted line. The periphery Sinis then obtained.

In some practical cases a still greater flexibility of such containersmaybe attained if the angle of intersection between the periphery andthe radius vector is 'in average chosen somewhat greater than 45, forinstance 46.

In'the case of'flexible'contai'ners thehub'p'ortions of the walls whichin most cases have a'c'ircular. oval or the like shape may be replacedby a polygon, from each side of which extend rectangular areas whoseouterside forms part of the periphery. This case is shown'in' Fig. 8 inwhich N denotes the circular hub of a flexible container wall which whendimensioning the marginal curve is replaced by a hexagon S. From thesides of the hexagon extend rectangular areas such as ABCD and AEFfGQandbetween the adjacent outer cornersBand E'of neighboring'rectangles isinserted a uniformly curved portion of the peripheral curve. This'portion,"for instance, maycorrespo'nd to thecontourheveloped bycorrespondingly rounding ofi, frorn'the logarithmic spiral. In this-casein order to [prevent sharp points when rounding off' the peripheralcurve also such portions are employed in which theradius from'the'pointA intersects 'the periphery under According to Fig. 9 also -trapezoidalareas AIHD and AKLG'may be inserted, in which case a uniformly bentcurve portion inserted between the angles I and K. In this case theaverage value .is formed along the contour BIKE so that also in thiscase the rectangular areas ABCD and AEFG are not considered whenformingthe average value. If such rectangularly ortrapezoidally limited 7intermediate areas are employed when designing the container, acontinuously curved closed periphery cannot be attained, so that certainnon-uniform changes in the bending stresses occur in the tangentialdirection.

The possibility shown in Fig. 7, taking into consideration the hubareawhen dimensioning the container wall, is insufficient if the hub isrelatively large. If a uniformly bent periphery is to be obtained whileproviding a hub of relatively large diameter, the following way may befollowed:

For this consideration it is assumed that the hub is replaced by apolygon, and rectangular and triangular areas .of equal height are drawnon the polygon sides, the vertexes of the triangular areas lying on theperiphery of the wall plate, as Will be apparent from the discussion ofFig. 10 following later. The average value for each angle of the polygonis formed according to a contour line in which an angle of the rectangleon one of the polygon sides runs through the corresponding vertex of thetriangle to the vertex of the adjacent triangle and then to the triangleof the rectangle relative to the other polygon side, in which case thevaluesbelonging to the portions of contour line traversed in theopposite direction to that in which the periphery properis'traversed-must be considered with opposite signs. In this case thepolygon is so arranged that the vertexes of the two triangles belongingto a polygon angle lie at the points nearest and farthest from thecenter of the polygon and that the corresponding polygon sides areperpendicular to the line extending from the sides of the polygon to therespective vertexes of the triangles. The average value is formedaccording to the invention by considering the above-mentioned law forthe equalization of the angles.

Fig. 10 shows an embodiment of foregoing type. N denotes the circularhub area of a plate. The hub is replaced by an equilateral hexagon Swhich is so arranged that the two vertexes M and O of the triangles DMAand AOG respectively belonging to the polygon angle A lie at pointsnearest and farthest from the center of the polygon and that thecorresponding polygon sides AD and AG are perpendicular to the lines MPand OP. Between the points M and O is inserted a uniformly bentperipheral curve portion. This curve portion is shaped by consideringthe above-mentioned law for the formation of the average value which isformed along the trace B, M, O, E in the direction of the arrow. Thevalues corresponding to the rectilinear curve portions B, M and 0, E areto be considered in this calculation with opposite sign as the valuescorresponding to the marginal curve portion Fig. 11 shows a practicalembodiment of the invention in diagrammatic form in which is illustrateda domestic refrigerator equipped with a refrigerating apparatus of thecompressor type.

A container consisting of two flexible walls I and firmly secured to therefrigerator cab-met, whereas the hub 4 is connected with a rod 6movable in the upward and downward direction which is driven by acrank 1. The rod 6 is held by a guide 8 so that it carries out only anupward and downward movement upon the rotation of the crank I. The crankis driven by an electric motor 9 mounted on the top of the cabinet. Asuction conduit H and a pressure conduit 12 extend through the lower hub5. In the conduit II is arranged a suction valve l3 and in the conduitl2 a pressure valve l4. During the suction stroke of the compressor therefrigerant .is drawn into the working chamber of the compressor fromthe evaporator l5 shown schematically. through the suction conduit H andis forced into the condenser IB through the pressure conduit l2 duringthe compression stroke. The liquefied refrigerant collects in thecontainer I! in which is arranged a float valve l 8 and passes into theevaporator l5 through the conduit I9. For a better dissipation of theheat of condensation and of the heat liberated in the compressor and thedriving motor 9 a ventilator motor 20 is provided which supplies coolingair in the direction indicated by the arrows over the heat dissipatingparts of the set. The cooling air enters the hood 2! at the side wherethe condenser is arranged and leaves. the hood through air outlet ports22.

What is claimed is:

1. A member of a fluid system comprising a container of variable volumehaving two congruously shaped flexible walls connected with each I otheralong their periphery, said walls having a uniformly bent peripheralcurve forming with the radius vector an angle of intersection averaging45, said curve composed of individual portions of a logarithmic spiralforming with the radius vector an angle of intersection of approximately45, and rounding-01f portions connecting said spiral portions, saidrounding-off portions having parts forming with the radius vector anangle of intersection smaller than 45 allotted to parts forming an angleof intersection. greater than 45 so that the average angle ofintersection of said rounding-off portions also amounts to approximately45.

2. A member of a fluid system, comprising a container of variable volumehaving two opposite walls consisting of flexible plates of flat shapehaving a polygonal hub area, a plurality of rectangular areas extendingradially from said hub area, and a quadrangular area located betweeneach pair of neighboring rectangular areas and forming a tip projectingradially over said rectangular areas, said projecting rectangular areahaving its sides which form part of the periphery of said platesdesigned to intersect the radius vector with an angle amounting to 45average.

3. As a member of a fluid system, a container of variable volumecomprising two opposite flexible walls joined with each other alongtheir periphery and having a substantially plane shape with their centerareas substantially in contact with each other at the end of thepressure stroke of the container, said walls having a peripheral curveforming with the radius vector an angle of intersection averaging 45, apolygonal hub area, and equilateral triangular areas of two differentheights radially extending from the sides of said polygonal area andhaving their vertexes lying alternately on the nearest and farthestpoints respectively of said peripheral curve as distanced from thecenter of said polygonal area, the portion of said peripheral curveconnecting adjacent vertexes being uniformly bent so as to run outwardlyfrom a rectangle: circumscribed to and having a common basis with eachof said lower equilateral triangular areas and inwardly from the topside of a rectangle circumscribed to and having a common basis with eachof said higher triangular areas, the curvature of said peripheral curvenear the top sides of said rectangles compensating each other so thatthe greater angle of intersection with the radius vector near the lowerrectangles compensates for the smaller angle of intersection near thehigher rectangles so as'to result in said average angle of 45.

LAs a member of a fluid system, an expansible container composed of tWocongruous flexible wall plates arranged in face-to-face relationship andhaving a peripheral curve forming with the :radius vector an angle ofintersection of 45 average, said flexible wall plates being tightlysealed to .each other along said peripheral curve andhaving a flat andplane shape when in relaxed position so as to have the tendency to havetheir central portions contact each other while permitting said centralportions relative movements away from each other against said tendency.

5. As a member of a fluid system, an expansible container having twoopposite congruous flexible walls sealed to each other along theirperiphery and having a fiat and plane shape when in relaxed positionsoas to have the tendency to keep their central portions in contact witheach other while permitting said central portions relativemovements-away from each other against said tendency, said walls havinga peripheral curve which comprises rectilinear portions formingoutwardly pointing triangles, said rectilinear portions being-arrangedto form with the radius vector bisecting the angle at the vertex of.said triangles an angle of intersection of average.

6. As amember of a fluid system, an expansible container having twoopposite congruous flexible walls sealed to each other along theirperiphery andhaving a fiat and plane shape when in relaxed position soas to have the tendency to keep their central portionsvin contact witheach other while permitting said'central portions relative movementsaway from each other against said tendency,lsaid walls having auniformly bent peripheral curve presenting a plurality of rounded tipsand forming with the radius vector an angle of intersection of 45average.

7. A member of a fluid system comprising a container of variable volumehaving two congruously shaped flexible walls consisting of flat platesand connected with each other along their periphery so as to have theirhub portions movablerelatively toeach other, said walls having aperipheral curve composed of portions forming with the radius vector anangle of intersection greater than 45 and portions forming an angle ofintersection smaller than 45, said latter portions. being arranged ascompensation with respect to said former portions so that the angle ofintersection between said curve and the radius vector amounts to 45average.

HERBERT MAASS.

